This invention relates to a forward acting stapler.
Forward acting staplers are known in the art, and have a handle which is pivoted at one end of a stapler body. The handle is pivoted downwardly with the hand of the user received on an end of the handle remote from the pivot point. This end is generally vertically spaced above the location where a plunger and knife combination will drive a staple or nail into a workpiece. For purposes of this application, the term xe2x80x9cplungerxe2x80x9d should be understood to also include the knife which moves with the plunger. The forward acting stapler is an improvement over staplers which have the pivot point of the handle on the end of a stapler body which receives the plunger in that the force of the hand can be applied more directly to the plunger.
In the prior art, such forward acting staplers have been known for decades. However, the forward acting staplers known to date have had complex linkages which have made them difficult to use and sometimes unreliable.
The present invention provides a linkage including a handle lever which is connected by a pair of links to a trigger lever. In fact, each of the links have two sides which are positioned on each side of the handle lever in a preferred embodiment. The trigger lever is controlled to pivot as the firing handle is pivoted downwardly. The trigger lever has a trigger portion adjacent the end of the housing which receives the firing plunger. The two-part linkage between the handle lever and the trigger lever includes a first link pinned to the handle lever and which moves a roller. The roller is also fixed to a holding link which is pivotally attached to the housing. The roller is received in a slot in the trigger lever. The arrangement of the two links, the handle lever, and the trigger lever slot is such that as the handle lever is moved downwardly, the first link forces the roller to move in a direction to pivot the trigger lever in such a way that the trigger portion at the end of the trigger lever moves in a direction upwardly. When this movement occurs, the holding link causes the roller to move within the slot in a direction away from a pivot point of the trigger lever. The trigger portion of the trigger lever includes a member which is spring biased to a holding position at which it is received under a ledge on an actuating plunger. A flat power spring extends through the body of the stapler and biases the plunger to drive a staple or nail into a work surface once the plunger is released by the trigger lever.
As the handle is moved downwardly, the movement between the two links and the two levers continues with the trigger portion of the trigger lever continuing to pull the plunger upwardly against the force of the spring. During this movement, the geometry of the trigger portion tends to move the trigger away from the plunger. At some point, the power spring drives the plunger to drive a staple into the workpiece.
In a preferred embodiment, the trigger portion is mounted near the end of the trigger lever on a pair of pins and a bias spring combination. One pin is fixed to the trigger lever and is received within a slot in the trigger portion. The trigger portion has its own pin received in a slot on the trigger lever. A spring biases the trigger portion pin toward the trigger lever pin, and thus biases the trigger portion outwardly toward the plunger. This spring force holds the trigger portion under the plunger as the plunger is raised, and up until the firing point. When the trigger lever is returned after firing, this spring allows the trigger portion to cam along a ramp surface on the plunger and be returned beneath the plunger ledge.
The present invention provides a reliable and simplified linkage. Further, the trigger portion is also simple and yet quite reliable.
The present invention can be best understood from the following specification and drawings, the following of which is a brief description.